Field of the Invention
This invention relates to a hydrostatic axial piston machine utilizing a bent-axis construction having a drive shaft located inside a housing and rotatable around an axis of rotation. The drive shaft has a drive flange. A cylinder barrel is located inside the housing of the axial piston machine and rotates around an axis of rotation. The cylinder barrel has a plurality of piston bores. A longitudinally displaceable piston is located in each piston bore. The pistons are fastened to the drive flange in an articulated manner. A drive joint for driving the cylinder barrel is located between the drive shaft and the cylinder barrel. The drive joint has at least one drive body in the form of a slider or roll body which is supported on the drive shaft and the cylinder barrel.
Description of Related Art
In hydrostatic axial piston machines utilizing a bent-axis construction, the longitudinally displaceable pistons located in the cylinder barrel are generally fastened to the drive flange of the drive shaft by a ball joint. The piston forces are transmitted by the piston to the drive flange located on the drive shaft and generate a torque. In axial piston machines utilizing a bent-axis construction, during rotation there is theoretically no drive of the cylinder barrel with the pistons located in it. For driving of the cylinder barrel, a drive joint is necessary and is located between the drive shaft and the cylinder barrel. A drive joint that employs the Rzeppa principle or the tripod principle can be used, in which the cylinder barrel is driven by at least one drive body in the form of a roll body or a slider that transmits a torque between the drive shaft and the cylinder barrel for driving the cylinder barrel.
Generic axial piston machines employing a bent-axis construction have significantly higher maximum allowable speeds of rotation than axial piston machines utilizing a swashplate construction. Thus, axial piston machines utilizing a bent axis construction have advantages for use as a hydraulic motor.
In hydrostatic axial piston machines, the housing inside which the rotating drive shaft and the rotating cylinder barrel are located is filled with a pressure medium, such as hydraulic oil, to provide cooling and lubrication of the components. During operation of the axial piston machine with a rotating drive shaft and rotating cylinder barrel, this arrangement results in churning losses that increase extra-proportionally as the speed of rotation increases. These churning losses represent an additional consumption of energy, which in an axial piston machine in the form of a pump must be compensated for by the drive system and result in an undesirable power loss, or in an axial piston machine in the form of a motor resulting in a lower output power. In particular, at high speeds of rotation of the rotating components, this power loss can be of a significant magnitude, as a result of which the efficiency and potential applications of axial piston machines at high speeds of rotation are limited and restricted.
To eliminate these disadvantages, the housing of the hydrostatic axial piston machine can be emptied of hydraulic fluid to reduce the losses caused by the churning of the rotating components and to increase the efficiency of the axial piston machine at higher speeds of rotation.
In a hydrostatic axial piston machine and with a housing emptied of hydraulic fluid, however, sufficient cooling and lubrication of the drive bodies of the drive joint are no longer guaranteed.
An object of this invention is to provide an axial piston machine that can be operated with a housing that has been emptied of hydraulic fluid and simultaneously guarantees sufficient lubrication and cooling of the drive bodies of the drive joint.